1. Field of the Invention
The present invention relates to a method of identifying food stuffs that are thawed and later refrozen. More specifically, the thawed and refrozen food stuffs are identified by the change of their physical appearance.
2. Description of the Related Art
Many food stuffs must be stored in continuously frozen condition to maintain their taste and quality. However, it is not uncommon that such frozen food stuffs are temporarily defrosted or thawed due to changes of the storage conditions, such as temperature change or changes of other environmental factors, and then they are refrozen when the storage conditions resume. Thawing or defrosting, even for a short period of time, may encourage the growth of bacteria or damage cell structures, which result in deterioration, spoilage and unfavorable odors and tastes. Sometimes, such adversely affected food stuffs are unfit for human consumption. Subsequent refreezing of the products usually will not remove such undesirable characteristics caused by thawing or defrosting.
While the thawed and refrozen food products may have lost their freshness, consumers or users of such food products usually are unable to determine whether such food products have been adversely affected by thawing or defrosting from their appearance.
Many devices and methods associated with such devices have been developed to indicate the thawing and defrosting process occurring during storage as a result of the changes of the storage conditions. Typically, these devices include a material which irreversibly changes its color, shape or other properties at or above a pre selected temperature such that such irreversible changes can be visualized .
U.S. Pat. No. 4,022,149 describes a thaw indicator, which comprises a capsule formed from an edible wax and filled by a mixture of edible gelatin and a colored liquid. The capsule is surrounded by a non-toxic blotter like absorbent material which is coextensive and in contact with at least a substantial portion of the outer surface. When the thaw indicator is frozen, along with the package, the mixture of gelatin and colored liquid expands enough so it cracks the edible wax capsule. While the mixture of gelatin and colored liquid is frozen, it can not be absorbed by the blotter-like absorbent material. When the temperature of the package rises above the pre-determined level for a predetermined period of time, the mixture melts and colored mixture is absorbed by the blotter-like material, staining it and providing a non-reversible indication that the contents of the package has been thawed or defrosted.
U.S. Pat. No. 4,114,443 teaches a freeze/thaw indicator having a container which comprises an upper transparent portion and a lower opaque portion provided with inward projections. Colored water can be frozen in place within the opaque portion. The projections hold the ice in place in the opaque portion of the container so that the extent of thawing is evidenced by the presence of water in the transparent portion of the container in the event of a rise in temperature in the freezer compartment.
U.S. Pat. No. 5,301,632 teaches a thaw indicator comprising a case or envelope, which is sealed in an inviolable manner and, in the case or envelope, a meltable object having a predetermined shape different from the internal shape of the case, this object has a melting point below or equal to the thawing or keeping temperature, of the product. The case is also partially transparent so that the meltable object can be seen through the transparent portion. Once the object melts, the original shape is irreversibly changed.
U.K. Patent Application Number G.B 2215460A describes a thaw indicator consists of a simple ice cube which is made from a mildly dyed water solution, placed in a clear plastic bag. The bag is then sealed and fitted into foodstuff packaging. The ice cube changes its shape if it melts.
All of the above described thaw indicators are made separately from the frozen products and can be easily removed from the package and replaced with a new one. In addition, most of these thaw indicators are not reusable and they usually have to be obtained from else where, which inevitably becomes too costly and inconvenient. Further, an indicator that is made in a material different from the frozen food product and placed separately from the frozen food product might not accurately reflect the actual frozen/thawed state of the frozen food product.
Accordingly, an object of the present invention is to provide a simple method identifying thawed and refrozen food products by the frozen food product itself, not by a separate indicator unrelated to the frozen food product.
Another object of the present invention is to provide a method of freezing a food product in connection with a mold where the food product is placed prior to the freezing process. The mold includes an inward projection that is capable of creating an indentation or a mark or a void on the food product in such a way that the indentation or the mark or the void cannot return to its original shape or condition after the frozen food product is thawed.